We have a particle of weight 40N attached to a string 1.2 m from a wall. The string is pivoted on a vertical wall and there is a force of magnitude F acting upwards on the string at a distance of 2m from the walls.
The particle is at equilibrium if the total torque in the system is zero. This is possible when 1.2 * 40 = 2 * F
=> F = 1.2 * 40 / 2
=> F = 0.6 * 40
=> F = 24 N
The magnitude of the force is 24 N.
The tension in the string is 40 N as the tension in the string added to the downward force exerted by the particle has to be equal to zero which is indicated by the lack of acceleration.